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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Imports"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import h5py\n",
"import matplotlib.pyplot as plt\n",
"import numpy as np"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Load Data"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"h = h5py.File('data.mat','r')\n",
"img = np.transpose(h.get('img')['real']+1j*h.get('img')['imag'])"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"6/8 Partial Fourier sampling"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"n = np.random.randn(96,96) + 1j*np.random.randn(96,96)\n",
"y = np.fft.fftshift(np.fft.fft2(img),axes=0) + n\n",
"y[72:,:] = 0"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Estimate phase"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"pad = np.pad(np.hanning(48),24,'constant')[:,None]\n",
"phs = np.exp(1j*np.angle(np.fft.ifft2(np.fft.ifftshift(y*pad,axes=0))))"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"POCS reconstruction"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"est = np.zeros((96,96))\n",
"iters = 10\n",
"for i in range(iters):\n",
" est = np.fft.fftshift(np.fft.fft2(est*phs),axes=0)\n",
" est[:72,:] = y[:72,:]\n",
" est = np.maximum(np.real(np.fft.ifft2(np.fft.ifftshift(est,axes=0))*np.conj(phs)),0)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Plot reconstruction"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"_, ax = plt.subplots(1,2,figsize=(16,16))\n",
"ax[0].imshow(np.abs(np.fft.ifft2(np.fft.ifftshift(y,axes=0))), vmin=0, vmax=1)\n",
"ax[0].set_title('Zero-filled')\n",
"ax[1].imshow(est, vmin=0, vmax=1)\n",
"ax[1].set_title('POCS recon')"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.7.3"
}
},
"nbformat": 4,
"nbformat_minor": 4
}